Undercurrent
by howlingmoonrise
Summary: AU where Seo is a siren and Wakamatsu is the son of a fisherman. Oneshot. (My very, *very* late contribution to SeoWaka Week.)


**A/N: In my first language (and many others), the terms for 'siren' and 'mermaid' are the same, so I use them here somewhat interchangeably. Enjoy!**

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* * *

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Wakamatsu Hirotaka had always had trouble sleeping.

At least, as far as he could remember - which was since when he was around five years old and his earliest memory was hearing the tale of a siren who lured sailors to their deaths. He had kept his eyes wide open at night, blanket pulled up as far as it would go, and he would think that he if he strained his hearing, he could almost hear her. Lorelei. The enchantress. The siren. _Her_.

He didn't dare think of her name too much, in case it she decided to sink his father's fishing ship as some sort of vengeance for her name constantly being on his thoughts, so she just became _her_. _Her,_ who would haunt his nightmares whenever he was too exhausted not to fall asleep; _her_ , who he found himself doodling absent-mindedly - rather shoddily too, as he didn't have an inch of artistic skill in his body - even though he had no idea what she actually looked like.

He told his father to always take earplugs when he went on a fishing trip, like he had read in a story, but after the eleventh time he had been dismissed with a quick laugh and a ruffle to his hair, he gave up. Instead, Wakamatsu went out to the shoreline on the night his father spent away from home, thinking that maybe he could draw her attention to him instead. His mother scolded him in the morning, when he returned soaked with sea spray and sneezing, and told him that he should stop even as she served him a hot breakfast.

But he couldn't bring himself to do it.

The shore had become a second home to him. Feet dipped in the salt water, sand swirling lazily around his toes as the tides came and went, the sun warming his face with breezy caresses more befitting of a lover.

He is seventeen when he decides to go with his father.

.

* * *

.

The wind whips at his face, stinging his eyes with salt as he opens them wide towards the storm clouds that rapidly approach.

"These weren't there earlier," his dad mutters to himself, and tells him to move to the lower deck while they deal with the ship.

Wakamatsu understands why he should go below deck, he really does. He's a hindrance to the crew, all seasoned sailors that surely have handled storms far worse than this one; if he sticks around he'll only be on their way, and could even slip over the railing and cause even more trouble for everyone involved. But something is calling out to him, an anxious churning in his gut that tells him to stay, _stay_ , that something isn't right, that something _is right_ , and he doesn't know whether to be afraid or not. But Wakamatsu is nothing but a sailor's son, so even if he doesn't go below deck like ordered, he still grabs a rope and ties it around his waist with sure, practised knots.

The wind leaves him nearly deaf with its strength, so loud that it could almost be confused with screaming or singing. Only it's not confusion, he thinks, because through the mist and the fog and the droplets of water that sting his face with rapid attacks, he thinks he sees a girl. Wakamatsu can't distinguish any features other than her paleness and and the green-gold of her hair and her voice - oh, her _voice -_ a voice that he can seem to hear even underwater.

Because he's underwater, he realizes with the last vestiges of consciousness. He's underwater, still bound to the ship with the rope he'd tied around himself, and his eyes sting and his body shivers with the cold, cold water that is entering his lungs.

And then there is gold.

And then there is nothing.

.

* * *

.

The summer sun is unrelenting, attacking his eyelids with heat until he is forced to open them just to stop them from burning. It doesn't help; they sting and burn and he finds himself blinking several times to diminish the pain and the blackness that dulls his vision. He expects to see a white roof, blue-painted walls, an open window with the curtains drawn back - something he'd complain to his sister for, since she had a tendency to impose her early-riser habits on the other house inhabitants.

Instead, there is only sea and sky and green-gold.

There is a girl, he realizes with the kind of slowness unique to those who have just awoken. There is a girl, with eyes that glint like amber and hair that spills over one shoulder like silky algae, the kind that grows on the tide pool rocks near his house. He feels dazed, lost. She's nearly naked, and he needs to think for a good moment to realize why that thought should bother him.

He needs another moment to realize that not knowing his own name should bother him even more.

"Sorry for intruding, miss," he says, and it's awkward and raspy and husky, and his throat stings from sea and salt and cold. And though he doesn't know where he is, or how he'd even get there if he knew, he adds, "I'll be going home now."

 _Cold._

 _Sea._

 _Salt._

There is a flash of memory from behind his eyelids, still squinting against the sun and the pale glow of the woman before him. There is rain, and darkness, and water pulling at him, pulling him _in_ \- or perhaps they were hands, small and delicate, dragging him away, cutting at the ropes that bound him. But the memory is gone as soon as it appears, and he feels dizzy.

There is a sweet, melodic voice filling the air, painting it with golden light that twists and curls, wrapping around every inch of his mind; Wakamatsu finds himself leaning forward, nearly falling on top of the woman that sings the song of the sea and the waves, and exhaustion claims him before he can say anything else.

.

* * *

.

When he wakes up, the summer sun is high in the sky once more, but it isn't burning at him. Wakamatsu finds himself in the shade, leaning against the rock walls of a tide pool, water up to the middle of his chest. The remainder of his clothes - the bits that weren't frayed or torn or just plain missing - chafe at his skin. One look is at the red, overly-sensitive skin is all he needs to determine that he has quite a severe sunburn, and that - coupled with a blinding headache and the dryness of his throat - tells him that he'll be in severe trouble if he doesn't get help soon.

Help comes quick, it turns out.

His sister comes running, chasing after a seagull that is holding something shiny in its beak. He barely realizes it's her, eyes squinted and burning against the breeze that assaults them, but it _is_ her and she's _there_ , kneeling by him and uncaring of the salt water that instantly wets the denim of her pants.

"Hiro! Hirotaka!" She grabs at his face, checks his pulse, and he's distantly aware that there are tears streaming down her face. "We thought you were-"

She chokes. _Dead._ The word rises to the surface of his brain, unbidden, even though it never makes its way past her lips.

His body is heavy, waterlogged as she does her best to drag him out of the tide pool, the rocks scratching and cutting even more into his skin and clothes. "My cellphone," she mutters to herself. "That damned seagull took it. I don't think I can get you out of here by myself."

Something glints at him from the corner of his eye, and he uses what little strength he has to turn his head and point, with his chin, towards it with the best of his ability. Whatever had brought the seagull towards him and led it to abandon its treasure, he was grateful.

His eyelids are heavy. Wakamatsu tries to keep them open, but they keep sliding shut, shielding him in the darkness of his mind. When he first closes them, his sister is speaking frantically into the phone, waving her free hand in his direction even though the person on the other side of the line most likely can't see him. The next time he opens them, she seems to have already finished the call, and is holding his head in her lap; she strokes his hair like she used to back when they all lived in the same house, when they were kids. The next, there is metal above his head and something holding him down, and people in white, nearly spotless uniforms talking all around him.

Then he stops keeping track, and everything is beautifully black.

.

* * *

.

When Wakamatsu wakes up, this time there is no sun in his face. Instead, there is blinding white all around - the walls, the ceiling, even the sheets are white, and a headache starts pounding at his skull when the brightness hits his eyes.

His mother is there, holding onto his hand and asleep. He distantly notices the puffiness of the area around his eyes and the tear-tracks dried in her cheeks; then guilt hits him like a tidal wave, even though he's still trying to remember why he feels guilty.

It doesn't matter, he decides. If his mother is crying and he's in a hospital, then surely it must have had something to do with him. That's enough to justify feeling guilty, regardless of what had actually happened.

His sister opens the door, a box of juice in each hand, and nearly drops them when she sees his eyes open.

"Aoi," he croaks out. "What am I doing here?"

.

* * *

.

If there is one thing Wakamatsu Hirotaka is grateful for, is that his dad is alive and well. The storm had left as quickly as it had arrived, and the one pressing matter left in the minds of the crew had been the disappearance of the youngest Wakamatsu. They believed him to be dead; his parents had been in the midst of preparing the memorial for their son - lost at sea, and he was so young, and it was so _heartbreaking_ that a week had gone by and they were still holding out hope instead of sending out orders for white lilies to place upon his empty grave - when his sister had called.

 _He's alive_ , she had said, and they had dropped everything with the most overwhelming and fragile of joys. She had found him on the other side of the coast, where she had moved after getting her first job; if it weren't for that damned seagull flying out with her cellphone she'd never had seen him, she said. The damned seagull had saved his life.

No one questioned why such a specimen of sea-fowl had developed such an interest in mobile electronics. Wakamatsu had given it a bit of thought himself, but why look a gift fish in the mouth? Or rescue, as was the case.

The one thing he wasn't grateful for, however, was the sheer _whiteness_ of the hospital. It had been a different way to start his stay at the hospital, but it had grown tiresome quite quickly. It was impersonal, unnatural, and the very colour seemed to fill his nose with the sharp smell of antiseptic.

He much rather preferred the sun.

.

* * *

.

He's out of the IVs and flavourless meals and the backless hospital gowns as soon as he's strong enough to walk out to the reception without having to catch his breath.

 _A week_ , they'd said. _A week_. He'd been missing for a whole, entire week, seven days as big as the universe when he barely remembered anything from after he'd fallen - jumped? been dragged? - out of the ship. It sounded impossible that he'd survived that long, out in the open sea in the middle of the storm, and then showing up in a place that someone from his family was sure to find him. It was impossible, but it had happened - he had been lost, starved, dehydrated, but so, _so_ alive -, so Wakamatsu forbids his mother to throw out his torn clothes and cherishes every new scar that had been birthed on his skin during that time.

 _You're not coming again,_ his father had said, and while Wakamatsu can't help but resent him for it, he also understands where he's coming from. To Wakamatsu Hirotaka, the sea is his home - a deadly mistress with loving arms, a comforting cradle with poisoned sheets - and it calls out to him, it _sings_ to him in shades of amber and green and gold and tells him to come back.

So he does.

He slips out of the house when his mother is preparing dinner and his brother is immersed in his most recently acquired videogame. His father has gone to drive his sister back to her own house - she has a job, a home, a life apart from them and every day her name is mentioned and she isn't there is a reminder of that - so Wakamatsu figures that this is the one chance he's going to get until his father's next fishing trip.

He's still weak from being lost at sea for a week, and then the time spent in the hospital. His legs aren't used to supporting his weight anymore, so even though he lives quite close to the shore, all the breaks he needs to take in order to make his head stop spinning lengthen his walk to nearly an hour.

Sand gradually starts mixing in with the dirt under his feet, and soon enough there's only sand, and sun, and sea.

He doesn't know what he had been expecting, but he knows it isn't _there_ when he gets to the beach. It's empty at this time of the year; it's still quite cold though the sun is out, and at most he'd been expecting a stray couple walking their dog. But it's empty, devoid of any presence but his, and he feels oddly disappointed though he's not sure _why_.

Regardless, he wanders down to the place where the salt water meets the sand, shoes and socks removed with a speed that amounts to years of practice, and he allows the cold sea to tug at the sand under his toes, burying them slightly; he feels goosebumps break out across his skin.

Wakamatsu has missed the sea.

.

* * *

.

He tries not to feel resentful when his father leaves on another fishing trip and leaves him behind. He fails.

Still, Wakamatsu Hirotaka isn't the kind of guy that allows resentfulness to stop him from _caring_ , so he heads down to the beach anyway, in his little ritual that has existed for as long as he can remember.

 _Be safe_ , he prays to the sea. And to _her_ , he says, _I am here, come and get me instead._

"Yo," says a female voice to his left, and he nearly shits his pants.

He tries to turn and trips in the process; a mouthful of sand greets him when he meets the ground. When he look up, there is a _girl_ , and she's laughing her ass off at him.

Not that he's looking at her ass. In fact, it would be a pretty much impossible thing to do even if he wanted to, which he does _not_ , since half her body is hidden by rock.

She waves off his attempts at standing up. "Oh, don't bother," she says, and he narrows his eyes at her. "You'll just end up eating sand again. Real graceful, you are."

Wakamatsu sits up anyway, just to prove a point. He doesn't try to stand up because he doesn't want to fall on his face again and prove _her_ point.

"Who are you?" he demands, or tries to, but it comes out sounding like a rather polite question. Damn his manners.

She waves her hand again. "Call me Seo. Or Yuzuki. Or L-" Then she side-eyes him, and doesn't tell him what else he can call her. "You're Waka, right?"

He stiffens. "My name is Wakamatsu Hirotaka, Seo-san."

Seo points at him. "Waka."

 _No._ He points at himself. "Wakamatsu."

"Waka."

 _This is going nowhere_.

"Yu-chan." He feels like dying as soon as the words leave his mouth. His face burns. "Never mind." He's too embarrassed to call her anything else.

She nods to herself, as if she hadn't heard a word from him. "Waka."

He resigns himself to his fate.

"So," she drawls, leaning further in the rock. "What are you doing here?"

"I live nearby," he says, knowing that he wasn't actually answering her question.

"You're not actually answering my question," she says, and his eyes widen.

"Are you a psychic, Seo-san?!"

"What." She says it so flatly that it's not even a question anymore. "What are you even talking about? Silly Waka."

He's so lost. So, _so_ lost. "Seo-san, you're confusing me."

She chooses that moment to dive back into the water, still hidden behind the rock. Moments later, she resurfaces, cheeks full.

He eyes her warily. "Seo-san, what are you-"

A stream of salt water hits him in the face. Even as he blusters angrily, he can't help but admire her impressive aim when spitting water at people.

"Seo-san!"

"Waka!"

"Stop calling me Waka!" It's like she's not even _listening!_

As if to prove his point, she splashes water at him.

"Now you're just being childish." He narrows his eyes as she sticks her tongue out.

"Come and swim with me, Waka!"

He kind of really _wants_ to, weird girl or not. He's a fisherman's son and he belongs in the waves; he misses them like he missed home. But Wakamatsu Hirotaka is nothing if not a sensible person, so he solemnly shakes his head. "I can't, Seo-san. I got out of the hospital a few weeks ago and I shouldn't even be out here by myself, much less swimming."

Seo raises an eyebrow at him. "You're not by yourself, though."

"I mean _with a responsible person_ , Seo-san."

To his relief, she drops it, shrugging nonchalantly. "Can't really argue with that."

They spend a few minutes in silence, which isn't too bad. Wakamatsu figures that as long as she's silent and standing still, she can't really bother anyone. But it also feels odd, like something that should be there is not, so he thinks of a way to get the conversation started again.

"Seo-san," he finally says. "Aren't you cold?"

She doesn't seem to realize that the warm summer waters are long gone; her only reaction is to look at him strangely, as if he had just asked something extremely nonsensical. "Why would I be cold?"

"It's no longer summer," Wakamatsu says, and he tries to focus on drawing tiny patterns on the sand around him with a stray stick. "The temperature's dropped. Haven't you noticed that no one else is around?"

The beach is, in fact, empty. Seo only seems to realize this now, lazily raising herself a little more on the rock as she looks around. She doesn't appear to be wearing a top, and he averts his eyes, blood rushing to his cheeks.

 _Don't look_ , he orders himself, vision swimming with glimpses of white, wet skin and green-gold hair. He doesn't realize he's shaking until she points it out.

"Hey," she says. "Are you okay?"

"No," he replies, because he isn't, not really. He thought he had recovered, but the smell of salt water can't seem to leave his nostrils even when he's not near the shore, and food and drink taste like algae and ocean as soon as they touch his tongue. He has suppressed it all into dreams and nightmares and thoughts that only come when his mind is too weak to keep away, and somehow this girl brings it all back to surface. "I'm sorry, Seo-san. I have to go."

He somehow manages to get himself up and standing, and he's walking away so fast that the ground tilts and whirls and he has to close his eyes in order not to fall down.

"Waka," he hears the girl say, voice sounding strangely melodic. "Come pray again soon."

He doesn't ask her how she knows, or why she's the only other person on the beach when the temperature is so low, or why her hair gleams green-gold under the dim sunlight. The only thing Wakamatsu can think is that _he needs to get out of there_ , and he makes it far enough into the way back that when he falls over and vomits, the only sea he can smell comes from his own mind.

.

* * *

.

He almost doesn't go back the next day.

But his father is still at sea and he won't be coming back any time soon, so he _needs_ to be down at the shore, praying, wishing, breathing in the salt and the ocean until it drowns away the incoherent flashes of memory that plague his mind.

Seo Yuzuki is not there when he arrives, and he almost wants to breathe out a sigh of relief. _Almost_. Because even though she calls to mind the things he's not sure he wants to remember and is a very difficult person to deal with, at least he's not alone. And if there is anyone that won't make fun of his ritual, it's probably her.

But she's not there, so he will do it alone.

 _Don't allow my father to find stormy waters_ , he prays. _If you really need someone to drown, come to me instead._

"Yo, Waka!"

He immediately flinches, a reflex before anything else. It's unexpected, and it startled him, but when he opens his eyes and she's _there_ , he finds that he doesn't really feel surprised.

"Seo-san," he greets, eyes wandering over her soaked form - or rather, the bits of it that aren't hidden behind rock and under the sea. Her green-gold hair is darkened with the weight of the water, and her eyes glint like amber under wet lashes.

He almost wants to go join her in the water.

"I almost thought you wouldn't show up," she muses, playing with her hair so that it lays only over one shoulder. Wakamatsu tries not to stare at the glistening skin of her newly bared neck. "You seemed rather distressed yesterday."

He swallows, ignoring how his ears fill with the sound of rushing water. He feels like he can't breathe. "It was a bit of a touchy subject for me."

"Oh?" She has a knowing half-smile playing on her lips, and he tries to focus on how she could possibly know anything about him instead of on the pink flesh. "Do tell."

He decides to sit down, because frankly, even if he wasn't still feeling a bit weak, talking to Seo is _exhausting._ "It wasn't anything you said, not really. It's just that being near the sea after- the _incident_ \- well. I kind of have a love-hate relationship with the ocean now."

She splays herself across the rock, and he can't help but imagine her with fins and a fish tail, curling lazily in the sun. He starts drawing a mermaid in the sand. "The incident?"

He swallows once, twice, three times. Anything to get the taste of salt out of his tongue. "I drowned a few weeks ago."

"You look remarkably well for someone who supposedly drowned." Wakamatsu doesn't miss the way her half-lidded eyes glance at his form; he shivers under her gaze.

"I- I can't tell you much about that, Seo-san. I don't remember most of it."

He thinks she looks a bit disappointed, but that can't be right. "None of it?"

" _Most_ of it," he corrects, trying not to be swept away by the bits and pieces of memory he's not quite managed to piece together yet. "I'd rather not talk about it, if possible."

"If you say so." She turns her disinterested eyes back to her hair, and he wonders if he annoyed her.

Minutes of silence pass by, and Wakamatsu begins to feel a bit antsy. _Come to me instead to him,_ he prays, just in case his previous words weren't enough.

"Would you stop that?" Seo says irritably. He looks up, confused, wondering if he had been doing anything to piss her off. "I'm already _here_."

He's so, _so_ lost. "I know you're here."

"Then stop calling for me!"

"I wasn't calling for any-" But he was, he remembers, and so his words slowly screech to a stop. "-one?"

 _Lorelei_. He hasn't thought of her name in so long, the mere thought of it seemingly dangerous enough; as soon as he thinks of it, he remembers. The summer sun, rock and sea beneath him, amber eyes and green-gold hair glinting in the light. _Lorelei._

He jumps to his feet, hands flying out to search for a weapon, _any weapon_ , but there isn't anything around he can use to defend himself with. "It's you," he breathes, because _how could he have forgotten?_

The flashes of memory are becoming more and more coherent as she looks at him, threatening to sweep him away. He remembers falling off the ship, still tied to it by a rope; enough to keep him there, but the added weight of him not allowing him to fight against the waves and the storm that surrounded him. He remembers dying, though he never got through with it; blue and grey mixing in an eerie pattern for his open eyes to see, light flashing above it; a shadow, a weight, warm against him as the constraints around his chest loosened and he suddenly became _free_. He remembers green-gold and amber and pale flesh, and a siren's song singing him to sleep.

Seo doesn't say anything. Her eyes fix him in place steadily as he nearly stumbles back; her gaze never wavers. She's waiting for something - he doesn't know quite _what_ she's waiting for, but he thinks he's starting to understand.

"You caused the storm," he says, but that's not all. "You _saved_ me."

She stays silent.

Wakamatsu nearly chokes again. His mouth fills with the taste of seaweed and salt water and he tries to ignore it. "Why?"

A sigh. His companion drags herself further up the rock, and he can see the fins, the scales, green-gold like her hair, and it's just like he had imagined. "I wanted to."

"You let lots of people die," he accuses, and it doesn't run through his mind that's he's confronting a creature that can control the seas and the skies with a simple melody. "I've heard the stories. _You caused the very storm that our ship went through._ Why me?"

She suddenly seems very shy, looking away from him and fixing her attention in her hair. "You're familiar to me."

"Familiar?" He's understanding less and less, and if there's one thing Wakamatsu Hirotaka despises, it's not understanding things.

"Yes." Seo meets his eyes straight on, all traces of what could have been shyness gone. "Or haven't you been praying to me for years?"

His blood runs cold.

"You heard all that?" He almost doesn't dare to ask.

"Why else do you think your father has never once run into a storm since you started doing it? The only time he did was when-"

"When I went with him." His eyes are wide; he can almost hear water rushing by his ears. "I didn't ask you to keep away that time."

"How was I supposed to know?" she asks softly, and that tone doesn't fit her at all. "I sing and call the storms as I feel like it, except when I'm asked not to. Nobody asked."

It's almost like she's justifying herself to him, and it doesn't sound right. He shakes his head. "I should have known better. I thought that since I was going-" He flushes, and doesn't end the sentence. "Well, I don't know what I thought."

She smirks devilishly, and Wakamatsu can't help but think that this look fits her much better than the softness of moments ago. "You thought you were a favourite of mine or something? Aw, Waka. Come here."

He doesn't remember _deciding_ to go, but between feeling flustered and trying to hide his embarrassed blushing, he's walking into the water before he even realizes it. The sea rushes into his sneakers and he's left with a squishy feeling in them. Ew. Wet socks. The cold water swirls around his legs as he walks in deeper, weakly trying to pull him in further.

"Waka," she beckons from her place in the rock, stretched out like a starfish, and he goes.

"Seo-san," he says, because he really isn't sure what else to do that doesn't involve staring at her partially uncovered chest, and _shit_ , he just walked into the water with a creature that controls the sea and _he didn't really think this through._

But she doesn't seem about to drown him or eat him alive or anything of the sort. In fact, she's stretching lazily on her and he has to look away _yet again_ because he's trying very hard to be a gentleman about this.

"Come here," she says, and he approaches hesitantly.

He does not expect the pair of very soft, very pink lips that land on his cheek, or the way her still-wet hair tickles at his jaw, or the loud cackle that she gives as she dives back into the sea on a very impressive jump for someone who has fins instead of legs.

He watches as the water dimples as she moves at deliriously fast speeds on it. She pops back out far away, far enough that he barely can distinguish her features, and she cups her hands around her mouth and yells, "Come and play with me again!"

He knows, without a doubt, that he won't.

.

* * *

.

He does. He absolutely does.

Wakamatsu Hirotaka decides that he's very, very bad at avoiding Yuzuki Seo. He has every intention _not_ to go, but really, it would be rude not to when she's expecting him, so he finds himself walking back to the shore time and time again, even when his father returns from the fishing trip unharmed.

She leaves him shells. He's not sure how she does it, how she manages to get so far to the sea as to reach him house, and infiltrate it, and find his room and leave them by his bedside table without him noticing or anyone waking up, but she does. They're pink, round and sharp, of all shapes and kinds imaginary, and they always smell of salt and sea; he can't help but remember that fleeting kiss on his cheek when he wakes up every morning and sees them.

He starts collecting them soon enough.

If he's acting any different, no one remarks on it. His legs - his body - gets stronger, back to what it used to be before he drowned and was rescued by _her_ \- and he wonders what exactly happened on that week that has been erased from his mind. He can make all the way to the beach without collapsing, now.

In exchange for the shells, he brings her pizza.

"Waka!" Her eyes shine when she sees him, and his gift. Her whole body seems to twitch in giddy delight. "You brought me pizza!"

He's puzzled. "You know what pizza is?"

"I go wandering around every now and then, Waka," she says dismissively as she starts munching on a slice, and he's left wondering how exactly she 'wanders around' when she very clearly doesn't have legs. Or _clothes_ , and he has to force himself to keep looking away.

"Would it kill you to at least wear a shell bikini?"

Seo gives him a weird look. "Why would I wear shells on my breasts?"

He splutters. "Seo-san! It would be the proper thing to do!"

" _You_ wear them if you find them so interesting."

Yeah, he's not replying to that. He eats his pizza slice moodily instead.

"But Seo-san," he says, once he finishes eating. "Don't you ever get cold?"

She eyes him like he just said something very stupid. "I control the oceans."

"Yes, but-"

" _Sea currents_. Warm currents. Plus, I'm cold-blooded."

"Oh." He's still musing over the shell bikini. "But couldn't you wear clothes? At least when you come to the surface?"

"Why would I?" She makes a point to stretch here, and _there his eyes go_ , staring again at inappropriate places. Wakamatsu mentally slaps himself.

"Because it'd be the proper thing to do."

"I don't particularly care about _proper,_ " she says, and Wakamatsu can't help but agree with her statement. "Clothes are annoying. Why?" Here her grin turns into a leer and Wakamatsu feels himself starting to blush. "Are you bothered, _Waka?_ "

"N-no."

She lets out a dramatic sigh. "I suppose that if you _really_ want me to wear clothes that much, I can do it. Though it _is_ quite a bother."

He quickly shovels another slice in his mouth to stop himself from saying anything that would bury him in embarrassment any further. He just _knows_ he'd say something stupid and which she'd take on an entirely different, far more mortifying way, so he figures it's best to just not say anything.

He wonders why he even bothers. But then again, Seo Yuzuki is like a hurricane, a storm, an undercurrent that won't let go; he is drawn to her again and again and again, and he's lost all hope of getting away.

.

* * *

.

One day, he falls sick.

He supposes that walking barefoot on the gelid winter waters is not the best attitude towards being healthy _and not sneezing his lungs out_ , but there are worse things. Like not being around Seo Yuzuki, or not breathing in the sea mist, or being stuck to bed when the thing he wants the most is to get up and walk to the shore. Oh, wait. _Right_.

He has just resigned himself to spending the day slurping down soup and staring wistfully at his shell collection when his window calls his name. That can't be right, he thinks, even if he does have a fever running.

"Waka!" calls the window again, only it's not the window. Seo Yuzuki is there, green and gold and amber and ivory and pink at his window, waving excitedly at him. He rubs his eyes, disbelieving.

"Seo-san?!" His fever must be higher than he had thought. "What- _How-_ "

"You weren't calling for me to come and play so I came to visit you instead!" She grins widely, seemingly ignoring his flushed cheeks and the enormous amount of dirty tissues spread all over his floor like sea foam.

He closes his eyes. He's too sick for this.

She seems to disagree.

"I'm coming in!" she cheerfully says, and he opens his eyes widely just in time to see two very nice, very shapely legs hoist themselves over his window. Um. Seo has legs. This is a new development. She's still not wearing clothes. This is _not_ a new development, and Wakamatsu feels his face burn even more. He tries to pretend it's because of the fever, knowing all too well it's not.

"Seo-san!" he whisper-yells, because he doesn't want to attract attention to his room, but also because he can't exactly use a normal tone of voice when there's a girl in his room and _she's not wearing any clothes_. "Put on some clothes!"

"Aw, Waka."

He fumbles with his hand on the floor near the bed until it grasps the edge of one of his shirts. He weakly throws it at her. " _Please_."

He turns to face the wall when the rustling of clothing starts, trying to be as respectful as he could possibly be on such a situation. Then, a thought occurs to him. He groans. "Seo-san, you didn't come naked all the way to my house, did you?"

She flops down on the bed beside him, now clad on his shirt. It's far too big on her; it slides down her shoulders, covering her all the way down to the middle of her thighs in a way that he really shouldn't be noticing but does anyway. "What if I did?"

He jolts to a sitting position, ignoring the way his vision swirls dangerously. "Seo-san-"

She forces him back down. "Relax, Waka. I'm not stupid. And _you_ are sick."

He can't really argue with that, so he allows himself to be pushed back down into the softness of his pillow. She strokes his hair almost affectionately - or so he likes to think - as she settles beside him, scales glinting at him from the place her legs are. He makes a mental note to ask her about them.

She starts singing, then; it's a low hum that quickly turns into a spoken melody, waves of golden voice filling the air, making their way into his head. He still tastes the sea on his tongue and hears water rushing in his ears, but it's almost comforting now.

He falls asleep with her hand in his hair and her voice in her ears, and it's the best sleep he's ever had.

.

* * *

.

Wakamatsu doesn't have trouble sleeping anymore, most days.

After that first night, there is a faint ringing on his ears. He wakes up feeling refreshed, not sick in the slightest, and even his mother shows surprise at this. She measures his temperature time and time again, keeps an eye on him all morning to see if there's a sneeze about to come out, suspicious of his sudden bout of health. It's not natural - even Wakamatsu has to agree with this much - but he's not about to go telling her that the Lorelei of the tales sung him to sleep (and back to health, apparently).

He dashes for the beach as soon as his mother is distracted.

"Seo-san," he calls, and then she's _there_ , looking at him with those amber eyes glittering in the winter sunlight.

"Waka," she greets back, offering him one of her too-wide smiles. "What's up?"

"You had legs yesterday," is the first thing that comes out of his mind. The second is, "Thank you."

She looks confused, and really, he can't blame her. "Thank you for having legs?"

He runs a hand through his hair. "N-no, I-" He takes a deep breath. "I wanted to thank you. For healing me, that is."

"Ah," she says, and her nose wrinkles as she smiles even wider. "No need to thank me. Who was I supposed to play with if you were sick?"

Wakamatsu has a feeling that she's embarrassed at being thanked, and decides to change the subject. "How did you grow legs, anyway?"

Seo shrugs, looking wholly unconcerned at something that should be physically impossible in theory. Wakamatsu thinks that controlling storms with songs should be physically impossible as well, but then again Seo Yuzuki is a very special kind of person. "I can do it if I feel like it. Staying in the sea all the time is boring; there's only so many ships you can sink before it loses most of its allure."

"Seo-san, don't speak like that of the people you drowned," Wakamatsu chides, wondering if he should be more concerned about these very people. "Just _please_ tell me you don't go wandering around naked."

She looks far too offended for someone who had showed up very much unclothed on his bedroom the previous night. "I _do_ understand society's expectations, Waka. I just prefer not to go by them most of the time. Here, watch."

He watches, because he doesn't really have much choice on the matter, as she dives elegantly out of her favoured spot on the rock and into the water. Then she is half-crawling, half-flopping herself out of the waves, dragging herself onto the sand beside him. Her scales glisten; he has a sudden urge to reach out with his hand and touch them.

"This is the worst part," she winces, and the scales start to fall apart right in front of his eyes. "Gross, and a bit painful, but fun to watch."

They peel away like dry skin after a sunburn, flaky and gross-looking when they come off, and sound interestingly like plastic wrap when they're touched. Under them there is some kind of slime coating tiny scales, tiny enough to be confused for human skin, and Wakamatsu realizes that all of her skin looks like that when seen up close. He also realizes that he's staring at her bare skin yet again. His throat feels dry.

"Seo-san," he says, an unspoken request lying underneath his words, and she nods. His hand is grabbed and being forced on the skin on her newly-formed knees, and he immediately winces at the sensation of slime against his fingers.

"Seo-san," he complains. "Gross!"

She cackles in response.

He plays with the slime between his fingers, trying to distract himself from the fact that, yet again, Seo Yuzuki is naked at his side. "Okay, you've made your point. About the legs, at least."

He can nearly _hear_ her rolling her eyes. "You still going on about the clothes? Jeez, Waka. It's not like I don't drown enough people to have clothes that fill an entire ship or anything."

He feels a twinge of _something_ \- not quite guilt, because he wasn't the one that caused it, not quite annoyance, because it's not their fault they had drawn her to them, perhaps pity? - towards all those that had not survived an encounter with his companion. "Seo-san," he asks, finally turning to look at her. "Why do you drown people?"

"Why don't you?" she playfully asks back, before her expression turns serious. "It's what we do."

"We?"

"Sirens; mermaids," she says, as if it should have been obvious. "It's an instinct more than anything else. There are ships that feel _right_ , and others that don't. Also, it's fun."

He tries not to complain. He really does. " _Seo-san._ "

She ruffles his hair affectionately. "Try not to get so affected by everything, Waka. You're going to be all wrinkly very soon if you keep at it."

Wakamatsu tries very hard not to pout.

But night comes soon enough, and he dreads going back to bed, to endless nights spent awake, to nightmares about drowning and getting lost at sea. They've gotten better after meeting the Lorelei of his thoughts, though, but they're still there, waiting to catch him unaware.

Only, he falls asleep, with the most melodious of voices singing into his ear even though he knows, _logically_ , that there's no one else in the room. Seo Yuzuki has infiltrated his mind, and she's not going back.

.

* * *

.

"Waka!" says a voice by his ear, too excited for such an early hour, and he opens one eye blearily. It's not his sister, as he expected, but then again there is only one person that calls him _Waka_.

"Seo-san," he groggily says. "What are you doing here?"

"Your mother let me in," she says rather cheerfully, and the words take a couple of seconds to register in his mind; when they do, he bolts upright.

The good part is that _she's wearing clothes_ , and he notices this with distinct relief. Wakamatsu has never been the religious type when it doesn't come to sea creatures, but he sends a _thank you_ to whichever deity might be listening.

The bad part? She's wearing _his_ clothes, and he knows _exactly_ what his mother is thinking after seeing her in them. He shivers in anticipation of the Girlfriend Lecture he's sure to receive as soon as Seo is gone.

She jumps in bed with him, and he tries not to think of all the other ways that sentence could be interpreted. He tries not to think of many things around Seo, he realizes, and it's quite a bother. "Seo-san, _what are you doing here_?"

"The water is warm," she says excitedly. "Warm enough for even _you_ to swim in."

He stares at her fixedly. "It's still spring."

She stares back. "It's _warm._ "

She wins. She always does.

They're making their way down to the shore soon enough, after Wakamatsu steers them around his mother and her knowing look. They haven't yet even made their way into the beach itself when she strips the shirt she's wearing and shoves it at him in one quick motion. The shorts follow after quickly - _and doesn't this woman understand the concept of underwear?_ \- and she's sprinting across the sand and into the ocean before he can even remember to avert his eyes.

"Feels good," she hums contentedly from the water, stretching languidly. "Clothes are itchy, even if they _are_ yours."

He's done trying to ignore his reactions to the things she says and does, and to Seo Yuzuki herself, so he doesn't pretend that the fact that she prefers his clothes doesn't affect him. "Are you sure the water is warm?"

She makes chicken noises. He has no idea how she even knows what a chicken is, but he decides that it shall remain one of the multiple mysteries of Seo Yuzuki. He quickly peels his shirt off as well, internally preening when her eyes track the movement and seem to linger more than necessary.

" _Fine_ ," he says, because he's done with all this. He hasn't been truly in the water since he had drowned, hasn't been swimming or holding his breath under the waves or diving in the depths since then, and he's tired of it. "I'm coming in."

It doesn't run through his mind that he's about to enter the water with a mythical creature said to drown and eat men yet again, or that the predatory glint in her eyes might mean more than simple interest or desire. He swims all the way to her, arms slicing through the water in strong, clean motions, and whips out of the water nearly out of breath.

"I'm a bit out of practice with the breathing," he says, laughing. He's far too conscious of how near she is to him, so it comes out nervous, almost forced. There are drops of water clinging to her lashes, and the shimmery scales of her skin make her look even more alluring than usual.

"Waka," she says, and he finds himself leaning in slightly - only for his face to meet water.

She splashes him again, cackling maniacally. "Catch me if you can!"

There's really no way that he can catch her, not when she's reverted back to having fins and has the speed of a shark going in for the kill, but he decides to amuse her and gives chase. They splash around the rocks and the sand, mostly playing, but Wakamatsu feels like there is something else at play here, something that he doesn't understand, something _primal_.

Her teeth glint from behind her lips, the flesh far redder and puffier than usual, and he suddenly _does_ understand. Seo unexpectedly allows herself to be caught - perhaps reading the dawning comprehension in his eyes, perhaps getting tired of their game - and they crash together into the water.

It surrounds him; it surrounds them both. Water _is_ rushing around his ears for real now, and there really is blue shades of everything when he opens his eyes, and there is the taste of salt in his tongue, and it's all real now. But also, there are green-gold caressing his skin, and amber eyes that are looking into his, and a softness against his lips that is too obvious for him not to know what it is. It scares him, but there's a different kind of adrenaline running through his veins now, and he brings his companion closer.

This is different. He's dreamed many times of Lorelei, of sirens, of drowning at the sea, but none of them can even compare to this. Her teeth pull at his lower lip a little painfully, but he _wants_ them to, so he lets his hands slide down her sides instead of protesting. The sea enters his lungs, and he allows it, welcoming his oldest friend in as he pulls himself deeper, _deeper_ , until all he can taste is the salt and the sea and Seo Yuzuki.

 _Sirens will sink you and eat you_ , he had heard since he was little. But also, _a mermaid's kiss will stop a man from drowning._

Surprisingly, miraculously, he doesn't drown. He resurfaces very much alive, even though he knows he's been down under long enough for anyone else to have survived, and Seo is still trapped within his arms and looking very much satisfied with herself. Or with him. He can never tell.

Her fin brushes up the side of thigh in a slow caress, and he stiffens.

Her smirk widens. "Still afraid of the big, bad Lorelei?"

"Seo-san," he says, because that's how he always speaks when it comes to her. "I'm now afraid of you for _entirely_ different reasons."


End file.
